The Casio fx-991ES PLUS is one of the most popular exam calculators in the world, so "is there a Casio fx-991ES PLUS online?" is a common search. The honest answer: yes for practice and homework, via browser emulators — but they differ in how faithfully they recreate the real thing.
On this page
Why use one online
- You own the physical unit but it's not with you.
- You're working on a laptop or phone and want the same workflow.
- You're learning the calculator's key sequences before an exam.
- You want to check homework answers quickly and for free.
What a true alternative must replicate
A graphing tool isn't a substitute — emulation means matching the actual machine:
- Natural textbook display for fractions, roots and integrals.
- The multi-mode engine — COMP, CMPLX, STAT, BASE-N, MATRIX, VECTOR, TABLE and EQN.
- SHIFT / ALPHA layered keypad so the key presses match.
- Angle modes (Deg / Rad / Grad) and the same function set.
The options
A faithful web emulator (this site)
A single-page fx-991ES PLUS emulator that recreates the keypad, natural display and all the main modes, free and offline-capable as a PWA. Closest to "the same calculator, in a tab."
Graphing tools (Desmos, GeoGebra)
Powerful and free, but a different paradigm — they don't emulate the Casio's keypad or its base-N and exam-mode workflow. Great companions, not replacements. (See Desmos vs Google vs a full scientific calculator.)
Other web emulators
Several exist; judge them by the replication checklist above — especially whether base-N, matrices and complex numbers actually work, not just the trig keys.
How they compare
| Need | This emulator | Desmos / GeoGebra |
|---|---|---|
| Same keypad & modes | Yes | No |
| Natural textbook display | Yes | Partial |
| Base-N & bitwise | Yes | No |
| Graphing | No | Yes |
| Free & offline (PWA) | Yes | Varies |
An honest caveat
An emulator recreates the experience but isn't the physical device. Some advanced behaviours can differ slightly, and online tools are not permitted in exams — use them for practice and checking. For everything this emulator can do, see the full documentation.
Frequently asked questions
Is there a Casio fx-991ES PLUS online?
Yes — browser emulators recreate its modes and keypad. This site is a free one covering all the main modes.
What should a good alternative replicate?
Natural display, the multi-mode engine, the SHIFT/ALPHA keypad, and angle-mode handling.
Are emulators allowed in exams?
Generally no — use them for practice, homework and checking.
Use the fx-991ES PLUS online
The same modes and keypad, free, in your browser — install it for offline use.
Open the fx-991ES PLUS emulator →